Flexible understructures for ground effect machines



Dec. 12, 1967 R, S. JONES 3,357,514

FLEXIBLE UNDERSTRUCTURES FOR GROUND EFFECT MACHINES Filed July 2, 1964 I 2 Sheets-Sheet 1 FIG. I

Dec. 12, 1967 s, JONES 3,357,514

FLEXIBLE UNDERSTRUCTURES FOR GROUND EFFECT MACHINES Filed July 2, 1964 2 Sheets-Sheet 2 United States Patent 3,357,514 FLEXIBLE UNDERSTRUCTURES FOR GROUND EFFECT MACHINES Richard Stanton Jones, Isle of Wight, England, assignor to Westland Aircraft Limited Filed July 2, 1964, Ser. No. 379,847 Claims priority, application Great Britain, July 20, 1963, 28,806/63 Claims. (Cl. 180-128) This invention relates to ground effect machines of the peripheral jet type, and is concerned with the construction of flexible skirt assemblies for such machines.

One of the problems encountered in the operation of such machines is that of retarding the outward escape of air from the ground effect air cushion so that, for a minimum expenditure of power to create and maintain the air feed, the optimum weight support, surface clearance or altitude, can be obtained. The problem is most important in relation to economical operation, since not only does the rate at which the air escapes from the cushion determine the minimum power requirements, it also governs the ground or water clearance ground effect machines can attain, and thus the surface conditions over which they can be operated without the hazard of damage to the lower structure.

To overcome these problems, flexible skirts attached at their upper ends to the lower periphery of the vehicle, and extending the inner and outer walls of the annular jet nozzle, have already been proposed. However, it has been necessary to provide these existing types of flexible jet skirting with full depth cross-diaphragms to maintain the desired form of the flexible skirting assembly and to maintain the inner and outer walls of such flexible skirts in the desired position relative to each other.

An object of this invention is to provide an improved construction of flexible skirting assembly, wherein the inner and outer walls of which assume a natural bulbous shape during operation, the assembly being substantially self-sustaining in shape, and in which the duct losses of air passing through the assembly are substantially reduced by the air being turned through a large cross-sectional area at relatively low velocity.

It has been discovered during extensive research and experimentation that flexible skirts made within the scope of this invention are very effective in operation.

According to the present invention a peripheral jet type ground effect machine is provided with an inflatable rflexible skirting assembly freely suspended to encompass at least part of, and to retard the escape of air or gas from, the gaseous ground effect cushion, the flexible skirting assembly comprising an outer flexible portion which, when the flexible skirting assembly is in the inflated condition, extends from its uppermost point of attachment to the ground effect machine outwardly from the gaseous cushion space, then downwardly and inwardly to include the outermost portion of a discharge nozzle arrangement, and an inner flexible skirt portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground effect machine downwardly and outwardly from the cushion space to include the innermost portion of said nozzle arrangement, said flexible skirting assembly having sufficient rigidity, when inflated, to assume and when deflected, to return to, a downwardly extended position, and means maintaining the innermost and outermost portions of the discharge nozzle arrangement in the desired position relative to each other.

In another aspect of the invention a peripheral jet type ground effect machine is provided with an inflatable flexible skirting assembly freely suspended to encompass at least part of, and to retard the escape of air or gas from,

Patented Dec. 12, 1967 the gaseous ground effect cushion, the flexible skirting assembly comprising an outer flexible portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground effect machine outwardly from the gaseous cushion space, then downwardly and inwardly to include the outermost portion of a discharge nozzle arrangement, and an inner flexible skirt portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground effect machine downwardly and outwardly from the cushion space to include the innermost portion of said nozzle arrangement, said flexible skirting assembly having sufficient rigidity, when inflated, to assume and when deflected, to return to, a downwardly extended position, and means maintaining the lower portions of the inner and outer skirts in the desired position relative to each other, the area enclosed by the nozzles being greater than the planform area of the rigid structure of the ground effect machine upon which the air cushion acts.

Further objects and advantages of the invention will become apparent from the following detailed description with reference to the accompanying drawings, which are by Way of example only, and wherein:

FIGURE 1 is an elevation in section through a portion of a ground effect machine where the sides are straight in planform, showing the ducting, flexible skirting and nozzles according to the invention.

FIGURE 2 is an elevation in section through a portion of the base platform of a ground effect machine where the sides are curved in planform showing the ducting, flexible skirting assembly and nozzles according to the invention.

In carrying the invention into effect according to one convenient form, the rigid base platform 1 of a peripheral jet type ground effect machine incorporates an air or gas supply duct 2 around its periphery, the air or gas supply duct 2 being formed by the rigid base platform 1 and a rigid outer casing 3. The duct 2 is flexibly extended a predetermined distance beneath the platform 1 by a flexible skirting assembly, generally indicated at 4, the predeter mined distance being chosen in accordance with the op erational role of the vehicle. The flexible skirting assembly 4 comprises a flexible outer wall or skirt 5 and a flexible inner wall or skirt 6, the outer wall or skirt 5 being attached to the rigid outer casing 3 at 7, and the inner wall or skirt 6 being attached to the rigid base platform v1 at 8. Air or gas, pressurised within the duct 2 by one or more fans, not shown, is directed through the duct 2 and discharged through the flexible jet nozzles, integrally formed in the base of the flexible skirting assembly 4, to generate the ground effect pressurised air cushion between the surface 9, over which the machine is operating, and the base platform 1. The flexible skirting assembly 4 is made of rubber, plastic, rubberised or plasticised fabric, or any other fluid-tight abrasion resistant flexible material.

The air channel formed by the flexible skirting assembly 4 is funnel shaped in cross-section, tapering towards the bottom, to form the flexible jet nozzle orifices, which are inwardly inclined to impart an inward component to the air being discharged. The pressure of the air or gas inflates the skirting assembly 4 and maintains the nozzles in their operational position and provides an element of sufficient rigidity to maintain and bias the flexible skirting assembly 4 in the downwardly extended position. Diaphragms 10, in combination with the inner skirt 6, form compartments 11, and tension in the diaphragms 10 maintains the inward inclination of the jet nozzle orifices. Flexible restraining membranes or crossdiaphragms 14 are provided between the inner skirt 6 and the outer skirt 5, and are located at substantially regular intervals along the flexible skirting assembly 4 tion relative to the inner walls of the flexible nozzles. The

lower ends of the opposed walls of the flexible nozzles may be retained in correct relationship with each other by chains 15. If desired, should chains 15 be utilised, they would be preferably located substantially in line with each adjacent pair of flexible restraining membranes or crossdiaphragms 14. Furthermore, extra chains may be added between, if necessary.

The compartments 11 are in communication with the air channel or duct extension by way of ports 12, located in the inner. skirt 6, and are further in communication with the ground effect air cushion by way of discharge ports 13.

One particular feature of the present invention is that the maximum ratio of the shortest distance between the line joining the points 7 and 8 and the lowest tip of the flexible skirting assembly (e.g. the point C in FIGURE 1), to the distance between the points 7 and 8 lies be tween 0.9 and 1.25. The point 8 may be located inboard of the air or gas supply duct, 2, as shown in FIGURE 1, or alternatively may be the inboard lower edge of the air or gas supply duct 2 as shown in FIGURE 2.

In operation of the invention, when the peripheral jet type ground effect machine is supported by the ground effect air cushion, the desired form of straight'sections of the flexible. skirting assembly 4, which are self-supportin g and receive no additional inherent stiffness that might be imparted by the portion of the platform that is curved in planform, is substantially as shown in FIGURE 1.

In this condition the inner wall or skirt 6 and the outer wall or skirt 5 assume radii substantially inversely proportional to the differential pressures across them, and the relationship between the radii assumed is given by the following formula:

r is the radius assumed by the outer wall or skirt. 1', is the radius assumed by the inner wall or skirt. P is the skirt mean internal pressure.

p is the cushion pressure.

K is a factor having a value between 0.75 and 1.0.

If the flexible skirting assembly 4 has some inherent stiffness imparted to it, because that part of the flexible skirting assembly 4 is suspended from a curved portion of the rigid base platform, then the inner and outer skirts or walls 5 and 6 will assume greater radii than in the case where there is no inherent stiffness imparted to it. Such a condition is illustrated in FIGURE 2. In general, as the inherent stiffness imparted to the skirting assembly by the curved portion of the rigid structure increases, the radii assumed by the inner and outer walls or skirts of the flexible skirting assembly increase.

When the peripheral jet type ground effect machine is performing translational movement in the water, the majority of the flexible skirting assembly is immersed in the water, and water will, therefore, collect in the air channel and the compartments 11. Upon transition to the normal cruising condition, when the machine is supported upon the ground effect air cushion, air or gas is caused to flow in the duct 2 as previously described, and the water passes through the flexible jet nozzle orifice under the action of gravity, assisted by the pressurised air or gas flowing in the duct 2. Until the level of the water in the air channel is below the ports 12, some of the water will pass into the compartments 11 and out through discharge ports 13, As the level of the water in the air channel or duct extension falls below ports 12, the pressurised air or gas flows into the compartments 11, by way of ports 12 forcing out any remaining water. It will be appreciated by those skilled in the art, that for eflicient operation of peripheral jet type ground effect machines, it is desirable to discharge, as speedily as possible,

any water that has collected in the flexible skirting assembly 4.

To improve the economical operation of a ground effect vehicle it is desirable to provide as large an air cushion area as is practicable for a given payload carrying area, and therefore the cushion area enclosed by the jet nozzles is preferably greater than the planform area of the rigid structure of the ground effect machine upon which the air acts.

The flexible skirting, when inflated, forms a pressure chamber and is sufliciently flaccid to permit it to fold locally to pass over an obstacle.

As shown in the drawings accompanying the specification, point 7 to which the outer wall 5 of the flexible skirting assembly is attached, is laterally outboard of the rigid structure upon which the air cushion acts, and it is preferred that at least part of the inner wall 6 encompasses a downwardly progressively larger planform area of the cushion.

Although the preferred embodiment hereinbefore described states that the outer casing 3 is rigid it is to be understood that this casing may be formed of flexible material supported in any convenient manner.

I claim as my invention:

1. A peripheral jet type ground effect machine provided with an inflatable flexible skirting assembly freely suspended to encompass at least part of, and to retard the escape of air or gas from, the gaseous ground effect cushion, the flexible skirting assembly comprising an outer flexible portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground effect machine outwardly from the gaseous cushion space, then downwardly and inwardly to include the outermost portion of a discharge nozzle arrangement which includes, at least one gaseous fluid discharge orifice, and an inner flexible skirt portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground effect machine downwardly and outwardly from the cushion space to include the innermost portion of said nozzle arrangement, said flexible skirting assembly having sufficient rigidity, when inflated, to assume, and when deflected, to return to, a downwardly extended position, and tension members maintaining the innermost and outermost portions of the discharge nozzle arrangement in the desired position relative to each other, the inner wall of said gaseous fluid discharge orifice or orifices being connected by tension members to the flexible inner skirt portion.

2. A peripheral jet type ground effect machine, as claimed in claim 1, wherein the tension members connecting the inner wall of the orifice to the inner skirt portion comprise flexible diaphragms which, with the flexible inner skirt portions, cooperate to form compartments, each compartment being provided with at least one port in communication with the interior of the pressurized air or gas cushion, and through which water that collects in the flexible skirting assembly is discharged, and at least one hole through the flexible inner portion of the flexible skirting assembly, through which the interior of the compartment is in communication with the interior of said flexible skirting assembly.

3..A peripheral jet type ground effect machine as claimed in claim 1, characterized in that when the flexible skirting assembly is inflated, it adopts a shape in which the inner and outer skirt portions assume radii substantially inversely proportional to the differential pressure across them, and the flexible nozzle arrangements take up a position such that their outer walls blend smoothly into the radii assumed by the outer skirt portion above them.

4. A machine as claimed in claim 1 wherein the ratio of the shortest distance between a line joining the points at which the inner and outer skirt portions are attached to rigid structure of the ground effect machine and the lowest tip of the flexible skirting assembly, to the distance between the points at which the inner and outer portions are attached to rigid structure of the ground effect machine, lies between 0.9 and 1.25.

5. A peripheral jet type ground eflect machine provided with an inflatable flexible skirting assembly freely suspended to encompass at least part of, and to retard the escape of air or gas from, the gaseous ground effect cushion, the flexible skirting assembly comprising an outer flexible portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground effect machine outwardly from the gaseous cushion space, then downwardly and inwardly to include the outermost portion of a discharge nozzle arrangement which includes at least one gaseous fluid discharge orifice, and an inner flexible skirt portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground effect machine downwardly and outwardly from the cushion space to include the innermost portion of said nozzle arrangement, said flexible skirting assembly having sufficient rigidity, when inflated, to assume, and when deflected, to return to, a downwardly extended position, and tension members maintaining the innermost and outermost portions of the discharge nozzle arrangement in the desired position relative to each other, at least part of the flexible skirting assembly depending from a portion of the periphery of the rigid base structure which is curved in plan, whereby said part of the flexible skirting assembly is stiffened partly by the eflect of circumferential stresses imparted to the skirting assembly by the curved portion of the rigid base structure and partly by the inflationary pressures within the skirting assembly.

6. A peripheral jet type ground effect machine as claimed in claim 5, wherein the greater the degree of stiffness imparted to the flexible skirting assembly by the effect of circumferential stresses, the greater the radii of the inner and outer skirt portions of the flexible skirting assembly.

7. A peripheral jet type ground eflect machine provided with an inflatable flexible skirting assembly freely suspended to encompass at least part of, and to retard the escape of air or gas from, the gaseous ground effect, the flexible skirting assembly comprising an outer flexible portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground effect machine outwardly from the gaseous cushion space, then downwardly and inwardly to include the outermost portion of a discharge nozzle arrangement which includes at least one gaseous fluid discharge orifice, and an inner flexible skirt portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground eflect machine downwardly and outwardly from the cushion space to include the innermost portion of said nozzle arrangement, said flexible skirting assembly having sufficient rigidity, when inflated, to assume, and when deflected, to return to, a downwardly extended position, and tension members maintaining the innermost and outermost portions of the discharge nozzle arrangement in the desired position relative to each other, the ratio of the shortest distance between a line joining the points at which the inner and outer skirt portions are attached to rigid structure of the ground effect machine and the lowest tip of the flexible skirting assembly, to the distance between the points at which the inner and outer portions are attached to rigid structure of the ground eflect machine, lying between 0,9 and 1.25, at least part of the flexible skirting assembly depending from a portion of the periphery of the rigid base structure which is curved in plan, whereby said part of the flexible skirting assembly is stiffened partly by the effect of circumferential stresses imparted to said skirting assembly by said portion and partly by the inflationary pressures within said skirting assembly.

8. A peripheral jet type ground eflect machine as claimed in claim 7, wherein the greater the degree of stiflness imparted to the flexible skirting assembly by the effect of circumferential stresses, the greater the radii of the inner and outer skirt portions of the flexible skirting assembly.

9. A peripheral jet ty-pe ground effect machine provided with an inflatable flexible skirting assembly freely suspended to encompass at least part of, and to retard the escape of air or gas from, the gaseous ground effect cushion, the flexible skirting assembly comprising an outer flexible portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground effect machine outwardly from the gaseous cushion space, then downwardly and inwardly to include the outermost portion of a discharge nozzle arrangement which includes at least one gaseous fluid discharge orifice, and an inner flexible skirt portion which, when the flexible skirting assembly is inflated, extends from its uppermost point of attachment to the ground effect machine downwardly and outwardly from the cushion space to include the innermost portion of said nozzle arrangement, said flexible skirting assembly having sufficient rigidity, when inflated, to assume, and when deflected, to return to, a downwardly extended position, and tension members maintaining the innermost and outermost portions of the discharge nozzle arrangement in the desired position relative to each other, the flexible skirting assembly when inflated adopting a shape in which the inner and outer skirt portions assume radii substantial- 1y inversely proportional to the differential pressure across them, and the flexible nozzle arrangement taking up a position such that their outer walls blend' smoothly into the radii assumed by the outer skirt portion above them, at least part of the flexible skirting assembly depending from a portion of the periphery of the rigid base structure which is curved in plan, whereby said part of the flexible skirting assembly is stiffened partly by the effect of circumferential stress imparted to said skirting assembly by said portion and partly by the inflationary pressures within said skirting assembly.

10. A peripheral jet type ground effect machine as claimed in claim 9, wherein the greater the degree of stiffness imparted to the flexible skirting assembly by the effect of circumferential stresses, the greater the radii of the inner and outer skirt portions of the flexible skirting assembly.

References Cited UNITED STATES PATENTS 3,117,645 1/1964 Cockerell 7 3,194,333 7/1965 Cockerell 1807 3,209,847 10/1965 Beardsley 1807 FOREIGN PATENTS 245,422 6/1963 Australia. 1,319,033 1/1963 France.

A. HARRY LEVY, Primary Examiner. BENJAMIN HERSH, Examiner. M. SALES, Assistant Examiner. 

1. A PERIPHERAL JET TYPE GROUND EFFECT MACHINE PROVIDED WITH AN INFLATABLE FLEXIBLE SKIRTING ASSEMBLY FREELY SUSPENDED TO ENCOMPASS AT LEAST PART OF, AND TO RETARD THE ESCAPE OF AIR OR GAS FROM, THE GASEOUS GROUND EFFECT CUSHION, THE FLEXIBLE SKIRTING ASSEMBLY COMPRISING AN OUTER FLEXIBLE PORTION WHICH, WHEN THE FLEXIBLE SKIRTING ASSEMBLY IS INFLATED, EXTENDS FROM ITS UPPERMOST POINT OF ATTACHMENT TO THE GROUND EFFECT MACHINE OUTWARDLY FROM THE GASEOUS CUSHION SPACE, THEN DOWNWARDLY AND INWARDLY TO INCLUDE THE OUTERMOST PORTION OF A DISCHARGE NOZZLE ARRANGEMENT WHICH INCLUDES AT LEAST ON GASEOUS FLUID DISCHARGE ORIFICE, AND AN INNER FLEXIBLE SKIRT PORTION WHICH, WHEN THE FLEXIBLE SKIRTING ASSEMBLY IS INFLATED, EXTENDS FROM ITS UPPERMOST POINT OF ATTACHMENT TO THE GROUND EFFECT MACHINE DOWNWARDLY AND OUTWARDLY FROM 